The present invention relates to swinging type centrifuge rotors and, more particularly, relates to a swinging carrier for a centrifuge rotor to support a microtitration plate.
In certain types of analysis work microtitration plates are utilized to determine the sedimentation characteristics of various fluid samples for evaluation to determine the content and/or characteristics of the particular fluid samples. The microtitration plate is one integral relatively thick plate made of plastic type of material and normally having nine rows of twelve cavities into which cells or other particles and serial dilutions of body fluids are directly placed. When it is necessary to utilize centrifugation to aid in estimating the amount of reactants in the precipitate or supernatant of these sample dilutions, the plate is placed in a rotor carrier for subjection to centrifugal forces induced during centrifugation.
Typically, the carrier arrangement is pivotally attached to hinge pins in the yoke of the rotor structure to allow for the pivoting of the microtitration plate from a generally horizontal orientation when the rotor is at rest to a vertical orientation during operational speeds of centrifugation. The carrier assembly has a frame unit made of sheet metal, such as aluminum, to which is welded a transverse support member that pivotally attaches the entire carrier assembly with the microtitration plate to the rotor hinge pins.
The carrier frame unit is welded to the support member. However, it is very difficult to ensure that the welds are perfect with no defects. Since one of the primary areas of presently used microtitration plate carriers subject to fatigue and failure during centrifugation is the weld joint, the welding must be extremely good in order to avoid failure. It is very costly to provide the necessary inspection of the welds. One of the primary reasons that the weld joints are subjected to extreme stress during centrifugation is due to the fact that the frame unit of sheet metal will be subjected to some deflection during centrifugation. In other words, the sides or upward extending hanger portions of the frame unit which attach to the support member will tend to deflect inward as the bottom surface of the frame unit is subjected to high centrifugal forces when carrying the microtitration plate.
The support member for presently used carrier assemblies is typically a hollow tubular member which is welded to the sheet aluminum material that forms U-shaped frame unit into which the microtitration plate is placed. A significant problem which occurs during centrifugation is the possibility that the overall carrier assembly may become shifted toward one of the hinge pins and away from the other opposing hinge pin in the yoke area of the rotor resulting in possible disengagement of the carrier assembly from the rotor frame. The stresses experienced by the rotor frame and its radially extending arms which form the yoke in some instances may result in total dimensional tolerance values which would be in conjunction with the tubular support member design sufficient enough to result in the carrier assembly becoming disengaged from the rotor frame. If such a circumstance would occur, it would result not only in damage to the fluid sample being subjected to centrifugation, but also considerable damage to the centrifuge.